Diet Soda Intake Increases Long Term Dementia Risk
New cohort data suggest metabolic health may shape the observed link between diet soda consumption and dementia
A long-running community study found that people who drank more than one diet soda per day had a much higher risk of developing dementia, but this association weakened after accounting for obesity and diabetes, suggesting metabolic health may be a key driver rather than diet soda alone.
Study Details
Researchers analyzed data from the Northern Manhattan Study, a population-based cohort designed to examine vascular and neurological outcomes over time. Participants were free of dementia at baseline and followed with detailed cognitive assessments.
The findings were published online in the Journal of Alzheimer’s Disease in January 2026 and add to a mixed body of evidence linking sweetened beverages to long-term brain health.
Methodology
The analysis included 947 adults with an average age of 64 years at enrollment. Beverage intake was assessed using a validated food-frequency questionnaire that captured both diet and regular soda consumption. Dementia outcomes were determined through standardized neuropsychological testing and functional assessments over follow-up.
Researchers adjusted for age, sex, education, race and ethnicity, and vascular risk factors, then conducted sensitivity analyses excluding participants with obesity or diabetes to explore possible reverse causation.
Key Findings
Drinking more than one diet soda per day was associated with a substantially higher risk of dementia compared with lower intake.
Each additional daily diet soda was linked to a stepwise increase in dementia risk after adjusting for demographic and vascular factors.
The association was observed in White and Black participants but not in Hispanic participants.
When individuals with obesity or diabetes were excluded, the elevated dementia risk was no longer statistically significant.
Regular sugar-sweetened soda was not significantly associated with dementia in this cohort.
Implications for Practice
For patients, these results suggest that diet soda should not be viewed as a neutral or protective substitute for sugary drinks when it comes to long-term brain health, especially in the context of metabolic disease. The findings reinforce the importance of addressing obesity and diabetes as central risk factors for cognitive decline.
For clinicians, the study highlights caution in interpreting diet soda as a direct cause of dementia. Instead, frequent diet soda intake may act as a marker of underlying metabolic risk or behavioral changes aimed at controlling weight or blood sugar. Counseling can focus on overall dietary patterns, metabolic health, and vascular risk reduction rather than singling out diet soda alone.
Importantly, the authors and external commentators agree that the evidence remains mixed and does not yet support firm clinical recommendations to avoid diet soda solely for dementia prevention.